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Abstract:

An airbag in which no choking occurs and which can be rapidly deployed. A
cushion section of the airbag internally accommodates a cylinder-type
inflator that includes an insertion hole for inserting the inflator from
an outside to an inside, and a diffuser into which the inflator is
inserted, and a diffuser having a tubular portion obtained by folding
back a section of cloth to form symmetrical portions with an upper base
formed by the folded back part and a lower base formed by adjacent ends
of the symmetrical portions. The cushion section is folded back at both
lateral sides of the along first folding lines that are substantially
orthogonal to a longitudinal direction of the diffuser.

Claims:

1. A knee airbag internally accommodating a cylinder-type inflator,
comprising: a cushion section; an insertion hole defined in the cushion
section for inserting the inflator from an outside to an inside of the
cushion section; and a diffuser located within the cushion section and
into which the inflator that has been inserted from the insertion hole is
inserted, the diffuser having a tubular portion obtained by folding a
hexagonal cloth back along a diagonal of the hexagonal cloth thereby
forming substantially congruent and left-right symmetrical trapezoidal
cloths by taking the diagonal as an upper base and sewing a portion
corresponding to a lower base of the trapezoidal cloths to a foundation
cloth of the cushion section, and the inflator being inserted into the
tubular portion adjacent to the lower base, wherein the cushion section
being folded back at both outer sides along creases that are
substantially orthogonal to the longitudinal direction of the diffuser
and located longitudinally beyond the lower base of the diffuser.

2. The knee airbag according to claim 1, wherein the creases obtained by
folding back are positioned longitudinally between both ends the upper
base of the diffuser.

3. A knee airbag in which a cylinder-type inflator is accommodated,
comprising a cushion section having an internal diffuser with outlet
ports defined therein, a roll section formed in the cushion section by
folding or winding in an accordion-like or roll-like configuration in the
knee airbag, and both ends of the roll section being folded back to a
center thereof to define folds, and the folds being formed in a position
wherein the outlet ports of the diffuser are not closed by the folds.

4. The knee airbag according to claim 3, wherein the folds are formed in
a position wherein the outlet ports of the diffuser are partially closed
by the folds.

5. An airbag internally accommodating a cylinder-type inflator, the
airbag being one of a knee airbag, a driver seat airbag, a passenger seat
airbag, a side airbag and a curtain airbag, the airbag comprising: a
cushion section having lateral sides; an insertion hole defined in the
cushion section for inserting the inflator from an outside to an inside
of the cushion section; and a diffuser located within the cushion section
and into which the inflator that has been inserted from the insertion
hole is inserted, the diffuser having a tubular portion obtained by
folding a cloth portion back along itself at an upper base thereby
forming substantially congruent cloth sections and sewing adjacent end
portion defining a lower base of the cloth sections to a foundation cloth
of the cushion section, and the inflator being inserted into the tubular
portion adjacent to the lower base, and the cushion section being folded
back at both lateral sides along creases that are substantially
orthogonal to the longitudinal direction of the diffuser and located
longitudinally beyond of the lower base of the diffuser.

6. The airbag according to claim 5, wherein the creases define a line
traversing through the upper base.

7. The airbag according to claim 5, wherein the creases define a line
traversing through the upper base but not the lower base.

8. The airbag according to claim 5, wherein the cloth portion is of a
rectangular shape.

9. The airbag according to claim 5, wherein the cloth portion is of a
hexagonal shape.

10. An airbag in which a cylinder-type inflator is accommodated, the
airbag being one of a knee airbag, a driver seat airbag, a passenger seat
airbag, a side airbag and a curtain airbag, the airbag comprising: a
cushion section having an internal diffuser with outlet ports defined
therein, a roll section formed in the cushion section by folding or
winding in an accordion-like or roll-like configuration in the airbag,
and both ends of the roll section being folded back to a center thereof
to define folds, and the folds being formed in a position wherein the
outlet ports of the diffuser are not closed by the folds.

11. The airbag according to claim 10, wherein the folds are formed in a
position wherein the outlet ports of the diffuser are partially closed by
the folds.

Description:

[0004] A knee airbag is an occupant restraining device that is inflated
and deployed in the vicinity of the occupant's knees when a vehicular
accident occurs. By providing the knee airbag, it is possible to protect
the occupant's knees from collision with the instrument panel and the
like.

[0005] The knee airbag is mainly accommodated below the instrument panel,
for example, inside the lower section of the steering column cover on the
driver's seat side of the vehicle. To enable the attachment in a limited
accommodation state, the knee airbag is compacted by folding or winding
and attached in this state. When an accident occurs, the knee airbag
receives the supply of gas from an inflator (gas generator) and is
inflated and deployed inward of the occupant cabin of the vehicle.

[0006] The knee airbag should be inflated and deployed within a space from
below the instrument panel to the occupant's knees. Since this space is
extremely narrow, the knees cannot be prevented from colliding with the
instrument panel, unless the inflation and deployment proceed rapidly.
Therefore, the knee airbag is configured by using such measures as a
folding method ensuring instantaneous deployment or a method enabling
smoother inflow of the gas.

[0007] For example, Japanese Patent Application Publication No.
2004-330959 discloses an occupant airbag device of a bag-body type for
protection of knees that is provided with an internal inflator inserted
into a substantially cylindrical diffuser (flow adjusting device).
According to this document, the first to third flow-adjusting openings of
different opening areas are formed in the diffuser, and by using those
openings, it is possible to deploy the knee-protecting airbag before the
deployment of the bag for head and chest protection.

[0008] With the technique such as described in the above mentioned
reference, the tubular diffuser has a large length, thereby making it
possible to guide the gas at an accordingly high speed in the desired
direction. Therefore, the airbag easily expands in the left-right
direction, which is the longitudinal direction of the diffuser, and the
deployment proceeds rapidly. However, outlet ports at both ends of such a
long diffuser are closed by folding when the airbag is accommodated,
thereby causing the so-called choking, that is, a state in which the gas
cannot be smoothly ejected from both ends of the tubular diffuser when
the airbag is inflated and deployed.

SUMMARY OF THE INVENTION

[0009] With the foregoing in view, it is an object of the present
invention to provide a knee airbag in which no choking occurs and which
can be rapidly deployed.

[0010] In order to resolve the abovementioned problem, the present
invention, in a representative configuration thereof, provides a knee
airbag internally accommodating a cylinder-type inflator, including: an
insertion hole for inserting the inflator from an outside to an inside;
and a diffuser into which the inflator that has been inserted from the
insertion hole is inserted, the diffuser having a tubular portion
obtained by folding back hexagonal cloths along any diagonal, stacking
the substantially congruent and left-right symmetrical trapezoidal cloths
by taking the diagonal as an upper base, and sewing a portion
corresponding to a lower base of the trapezoid to a foundation cloth, and
the inflator being inserted into the tubular portion close to the lower
base, wherein the diffuser is folded back at both outer sides of the
portion corresponding to the lower base of the diffuser along creases
that are substantially orthogonal to the longitudinal direction of the
diffuser.

[0011] With the above-described configuration, a knee airbag is obtained
in which no choking occurs and which is rapidly deployed. This is because
the lower base, which has a small length, does not engage with the
creases, and the inflator is inserted close to the lower base, as a
result of which the gas outlet ports are not closed.

[0012] The creases may be also positioned on the inner side of both ends
of the portion corresponding to the upper base of the diffuser.

[0013] With the above-described configuration, the upper base portions of
the diffuser engage with the folds. However, since the vicinity of the
lower base where the inflator is present is not engaged, no choking
occurs. Meanwhile, rapid deployment is ensured since the upper base
portions are increased in length in the course of engagement with the
folds.

[0014] In order to resolve the abovementioned problem, the present
invention, in a representative configuration thereof, provides a knee
airbag in which a cylinder-type inflator is accommodated in an internal
diffuser, wherein: a roll section is formed by folding or winding in an
accordion-like or roll-like configuration in the knee airbag, and both
ends of the roll section are folded back to a center, and outlet ports of
the diffuser are not engaged with the folds.

[0015] The present invention can provide a knee airbag in which no choking
occurs and which can be rapidly deployed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 illustrates an accommodation position of the knee airbag of
an embodiment of the present invention in a vehicle.

[0017] FIG. 2 is an exploded view of the knee airbag shown in FIG. 1.

[0018]FIG. 3 illustrates the deployment state of the cushion section
shown in FIG. 2.

[0019] FIGS. 4(a)-4(d) illustrate a deflector accommodating the inflator
shown in FIG. 3 with FIG. 4(b) being a view in the direction of arrow A
in FIG. 4(a), with FIG. 4(c) being a view in the direction of arrow B in
FIG. 4(b), and with FIG. 4(d) being a view in the direction of arrow C in
FIG. 4(b).

[0020] FIG. 5 illustrates how the inflator shown in FIG. 4 is inserted
together with the deflector from an insertion hole into the cushion
section shown in FIG. 3.

[0021]FIG. 6 is a view from the inside of the turned-over cushion section
shown in FIG. 3.

[0028] FIG. 11 further illustrates the process of folding the cushion
section shown in FIG. 10.

[0029]FIG. 12 illustrates the process of folding the cushion section
shown in FIG. 9 and is shown in which the cushion section is turned over
so that the roll section formed as shown in FIG. 11 faces the rear side
in the figure.

[0030] FIG. 13 further illustrates the process of folding the cushion
section shown in FIG. 12.

[0031] FIG. 14 illustrates the further process of folding the cushion
section shown in FIG. 13.

[0032]FIG. 15 further illustrates the process of folding the cushion
section shown in FIG. 14.

[0034]FIG. 17 illustrates the cushion section having an alternate
diffuser than the diffuser shown in FIG. 6.

[0035] FIG. 18 illustrates the cushion section having a further alternate
diffuser than the diffuser shown in FIG. 17.

DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be
described below in greater detail with reference to the appended
drawings. The dimensions, materials, and other specific numerical values
are exemplified to facilitate the understanding of the invention and are
not intended to limit the present invention, unless specifically
indicated otherwise. Meanwhile, in the description of the invention and
drawings, the elements having substantially the same function and
structure are denoted by the same reference numerals and the redundant
explanation thereof will be omitted. In addition, the elements that are
not directly related to the invention will not be shown.

[0037] FIG. 1 illustrates by way of example an accommodation position for
a knee airbag in a vehicle in an embodiment of the present invention. A
knee airbag 100 is accommodated below an instrument panel 102. The knee
airbag 100 of the present embodiment is designed for a driver seat and
accommodated below a steering column bar 104. When an impact is generated
in the event of collision or the like, the knee airbag 100 is inflated
and deployed inside the occupant cabin of the vehicle. The knee airbag
100 can be also used as an airbag for a passenger (such a configuration
is not shown in the figure).

[0038] FIG. 2 is an exploded view of the knee airbag shown in FIG. 1. As
shown in FIG. 2, the knee airbag 100 is configured to provide a folded
cushion section 110 in a space between a knee airbag cover 106 and a
housing 108.

[0039] The knee airbag cover 106 is exposed as an interior member inside
the vehicle. A tear line 112 that is cleaved when the cushion section 110
is inflated and deployed is cut on the inner side (cushion section 110
side) of the knee airbag cover 106.

[0040] The housing 108 is a box serving as an exterior part with respect
to the cushion section 110. The housing 108 encloses the cushion section
110 and is attached to the vehicle. A plurality of hook sections 114 for
attaching the knee airbag cover 106 is provided in the housing 108. The
housing 108 is preferably constituted by a highly rigid material in order
to support the inflating and deploying cushion section 110, and the
housing 108 of the present embodiment is made from a metal.

[0041] The housing 108 is provided with an inflator attachment hole 116
and a bolt hole 118. One end (connector 126 side) of an inflator 122 that
is inserted into the cushion section 110 is attached to the inflator
attachment hole 116. A stud bolt 130 and a fusion bolt 144 provided at
the inflator 122 are passed through the bolt hole 118 and fixed therein.

[0042] The cushion section 110 is a member that inflates and deploys to
protect the occupant. The cushion section 110 is compacted by folding and
winding and attached in such a state inside the housing 108. The cushion
section 110 is wrapped with a flap 120 for maintaining the folded state
thereof. The flap 120 is a thin fabric that can be easily torn by the
inflation and deployment of the cushion section 110. The inflator 122
serving as a source for supplying a gas for inflation and deployment is
inserted into the cushion section 110.

[0043]FIG. 3 illustrates the deployed state of the cushion section 110
shown in FIG. 2. As shown in FIG. 3, the cushion section 110 is formed by
sewing the foundation cloth constituting the front surface of the cushion
section on the front and rear sides.

[0044] The cushion section 110 is provided with an insertion hole 124 for
inserting, from the outside to the inside, the inflator 122 inserted into
a deflector 132. In a folded state of the cushion section 110, one end
(connector 126 side) of the inflator 122 is exposed from the insertion
hole 124 (see FIG. 2). After the cushion section 110 has been
accommodated in the housing 108, a wiring (not shown in the figure) for
an output signal is connected through the inflator attachment hole 116 to
the connector 126. The cushion section 110 is provided with a bolt hole
128, and the stud bolt 130 and the fusion bolt 144 of the inserted
inflator 122 can be exposed to the outside.

[0045] FIGS. 4(a)-(c) illustrate the deflector 132 accommodating the
inflator 122 shown in FIG. 3. FIG. 4(a) is an exploded view of the
deflector 132 and the inflator 122 shown in FIG. 3. FIG. 4(b) is a view
along an arrow A of the deflector 132 and the inflator 122 shown in FIG.
4(a). FIG. 4(c) is a view along an arrow B of the deflector 132 and the
inflator 122 shown in FIG. 4(b). FIG. 4(d) is a view along an arrow C
shown in FIG. 4(b).

[0046] As shown by way of example in FIG. 4(c), the inflator 122 is of a
cylinder type. The inflator 122 has an igniter and a gas-generating agent
inside thereof, and where an output signal is received from the connected
wiring (not shown in the figure), the igniter is actuated, the
gas-generating agent located around the igniter is instantaneously
burned, and a gas for airbag inflation and deployment is generated. The
generated gas is supplied into the cushion section 110 from a gas
ejection port 134 provided in the front surface of the inflator 122.

[0047] As shown by way of example in FIG. 4(b), the inflator 122 has the
stud bolt 130. The stud bolt 130 passes through the bolt hole 136 of the
deflector 132, the bolt hole 128 of the cushion section 110, and the bolt
hole 118 of the housing 108 and fastens the aforementioned components.

[0048] As shown in FIG. 4(b), the deflector 132 is a member that regulates
the flow of gas ejected from the inflator 122. In a state in which one
end of the inflator 122 is exposed, the deflector 132 accommodates at
least the gas ejection port 134.

[0049] An end section 138 of the deflector 132 on the fused bolt 144 side
has a tapered shape. Further, as shown in FIG. 4(c), the end section 138
is subjected to bending by which the distal end corner 140 is rounded. As
a result, the deflector can be smoothly inserted into the cushion section
110, without being hooked.

[0050] As shown in FIG. 4(c), the deflector 132 fixes the inflator 122 so
that the gas ejection port 134 of the inflator 122 is positioned
substantially in the center of the deflector in the longitudinal
direction thereof. The deflector 132 has a flow regulating portion 142
where the inflator 122 is not present, this portion serving to regulate
the gas flow. As a result of providing the flow regulating portion 142,
the gas flow is regulated in the longitudinal direction of the deflector
132 (width direction thereof inside the cushion section 110). The
deflector 132 is made from a metal and functions not only to regulate the
gas flow, but also to protect the cushion section 110 from the heat
generated by the gas.

[0051] As shown in FIG. 4(a), the deflector 132 is provided with the bolt
hole 136 through which the stud bolt 130 of the inflator 122 passes. The
deflector 132 is fixed, together with the inflator 122 and the cushion
section 110, by the stud bolt 130 to the housing 108 (see FIG. 2).
Furthermore, the deflector 132 has the fusion bolt 144 (see FIG. 4(b))
and is also fixed to the housing 108 by the fusion bolt.

[0052] FIG. 5 illustrates by way of example the state in which the
inflator 122 shown in FIG. 4 is inserted together with the deflector 132
from the insertion hole 124 into the cushion section 110 shown in FIG. 3.
The connector 126 is usually provided at one end of the inflator 122, and
a wiring for sending an external signal is connected to the igniter
located inside thereof. Therefore, as a result of positioning the
inflator 122 with respect to the deflector 132 by the stud bolt 130 of
the inflator and exposing one end of the inflator 122 from the deflector
132 and the cushion section 110, the wiring can be easily connected.
Meanwhile, because of the abovementioned positioning, the deflector 132
is provided with the flow regulating portion 142 where the inflator 122
is not present, this portion serving to regulate the gas flow.

[0053] In the present embodiment, by providing the deflector 132 with a
clutch 150, it is possible to accommodate the inflator 122 in a state in
which one end thereof is exposed, and fix the inflator 122 in a posture
aligned with the deflector 132 although there exists the flow regulating
portion 142 where the inflator 122 is not present. Therefore, when the
deflector 132 is inserted into the cushion portion 110, the inflator 122
can be reliably prevented from falling out of the deflector 132.

[0054] In FIG. 6, the cushion section 110 shown in FIG. 3 is turned over
and viewed from the inside thereof. Thus, the foundation cloth located on
the opposite side is omitted in the figure. A diffuser 152 having
inserted therein the inflator 122 and the deflector 132 that have been
inserted through the insertion hole 124 is provided on the rear side of a
foundation cloth 110A where the insertion hole 124 shown in FIG. 3 has
been provided. In FIG. 6, the insertion hole 124 and the deflector 132
(accommodating the inflator 122 inside thereof) are not seen and
therefore shown by broken lines. As a result of inserting the inflator
122 together with the deflector 132 into the diffuser 152, the flow of
gas supplied from the inflator 122 can be regulated in the left-right
direction in FIG. 6.

[0055] The foundation cloth 110A is provided with a first sewing line 154
and a second sewing line 156, and the insertion hole 124 is positioned
between the sewing lines.

[0056]FIG. 7 is an exploded view of the diffuser shown in FIG. 6. In FIG.
7, the inflator 122 and the deflector 132 are omitted. As shown in FIG.
7, the diffuser 152 is obtained by folding two diffuser cloths 152A, 152B
and inserting one folded cloth into another. A portion where the diffuser
cloths 152A, 152B are folded and overlapped is sewed to the foundation
cloth 110A by the first sewing line 154. As a result, the diffuser 152 is
provided with a double-wall tubular shape. In the present embodiment, the
diffuser 152 has a double-wall tubular shape, but the number of the
cloths can be increased and decreased and the diffuser may accordingly
have a single-wall tubular shape or a tubular wall constituted by three
or more walls.

[0057] The sewing procedure is described below. First, the overlapping
diffuser cloths 152A, 152B are sewed by the second sewing line 156 to the
inner side of the airbag body. Then, as shown in FIG. 7, the diffuser
cloths 152A, 152B are folded and sewed by the first sewing line 154. It
is not until the sewing with the first sewing line 154 that the diffuser
152 assumes a tubular shape.

[0058] The cloth on the side close to the foundation cloth 110A, from the
tubular portion 153 of the diffuser 152, is further sewed to the
foundation cloth 110A by the second sewing line 156.

[0059] The cloth 152B on the innermost side of the double-wall tubular
shape of the diffuser 152 has a guide member 160. The guide member 160
covers the insertion hole 124 by the surface continuing from the inner
surface (inner surface of the folded cloth 152B) of the diffuser 152. The
guide member 160 is sewed to the foundation cloth 110A by the first
sewing line 154.

[0060] FIG. 8 is a view of the cushion section 110, which is shown in FIG.
5, that is taken from the inside thereof. In the configuration described
hereinabove, the distal end of the inflator 122 (actually, the deflector
132 that accommodates the inflator 122) inserted from the insertion hole
124 hits the guide member 160 of the diffuser 152. The surface of the
guide member 160 that has been hit continues from the inner surface of
the diffuser 152 (inner surface of the folded cloth 152B). Therefore,
although the tubular portion 153 of the diffuser 152 is separated from
the insertion hole 124 (see FIG. 6 and FIG. 7) to prevent choking, where
the inflator 122 is inserted as shown in FIG. 8, the inflator 122 is
guided by the guide member 160 and can be inserted into the diffuser 152,
as shown in FIG. 6, without a deviation.

[0061] Since the guide member 160 of the diffuser 152 is a single-layer
cloth and is not of tubular shape, the guide member essentially cannot
function as the diffuser 152. Therefore, the guide member 160 does not
cause choking. However, the guide member 160 is sewed to the foundation
cloth 110A by the first sewing line 154. As a result, even though the
inserted inflator 122 and the deflector 132 collide, no displacement is
caused thereby, and the two can be guided by the inner surface of the
diffuser 152.

[0062] In the conventional configuration, the diffuser 152 is shortened
because of the choking problem. As a result, the diffuser 152 does not
overlap the insertion hole 124 and is disposed at a certain distance from
the insertion hole 124, thereby making it necessary to move and insert
the distal end of the inserted inflator 122 as far as the end portion of
the diffuser 152. In this case, the inflator 122 can erroneously deviate
to the outside of the diffuser 152, but the present embodiment resolves
this problem.

[0063] When the diffuser 152 is configured to have a multiwall tubular
shape in order to increase the strength of the diffuser 152, as in the
present embodiment, the inflator 122 should be inserted in the innermost
tube, that is, the diffuser cloth 152B. Accordingly, the diffuser cloth
152B on the innermost side is provided with the guide member 160. As a
result, it is possible to prevent not only the deviation of the inflator
122 to the outside of the diffuser 152, but also the penetration of the
inflator 122 into a gap between the multiple tubes (between the diffuser
cloths 152A, 152B) constituting the diffuser 152.

[0064] Further, as shown in FIG. 6, in the present embodiment, the tubular
portion 153 of the diffuser 152 has a rectangular cross section. The
tubular portion 153 is configured to have the rectangular cross section
in order to maximize the flow regulating action of the tubular portion
153 that essentially functions as a diffuser.

[0065] The specific feature of the present embodiment is that the airbag
accommodating the cylinder-type inflator inside thereof has the insertion
hole, essentially an opening, for inserting the inflator from the outside
to the inside of the airbag, thereby providing the diffuser forming a
semi-closed space and the guide portion that introduces the inflator to
the semi-closed space when the inflator is inserted.

[0066] The abovementioned guide member may be connected to the edge
portion of the opening so as to guide the inflator from the insertion
hole to the opening in a generally continuous manner.

[0067] The above-mentioned guide member may be provided such as to
generally overlap the insertion hole so as to guide the inflator from the
insertion hole to the opening in a generally continuous manner.

[0068] In FIGS. 9(a)-9(c), the cushion section 110 shown in FIG. 3 is
partially cut out and the inner surface of each chamber is exposed. FIG.
9(a) is a front view of the cushion section 110. FIG. 9(b) is a sectional
view along line D-D of the configuration shown in FIG. 9(a) in which the
cushion section 110 is cut by a second folding line 188. FIG. 9(c) is a
sectional view along line E-E of the configuration shown in FIG. 9(a) in
which the cushion section 110 is cut in the center. As shown in FIGS.
9(a)-9(c), the cushion section 110 is provided with three (first to
third) chambers 162, 164, 166. The first chamber 162 and the second
chamber 164 are of substantially rectangular shapes and are adjacent to
each other at a boundary (third sewing line 168) extending in the
longitudinal direction (left-right direction in FIG. 9) in which the two
chambers are of substantially equal dimensions.

[0069] The third chamber 166 is of a substantially trapezoidal shape
having an upper base (fourth sewing line 170) that is substantially equal
in size to the abovementioned longitudinal boundary and a lower base
(outer peripheral sewing line 154) that is shorter than the fourth sewing
line 170. The third chamber 166 is adjacent to the second chamber 164 at
the fourth sewing line 170. The third chamber 166 accommodates the
cylinder-type inflator 122 close to the first sewing line 154, the
inflator extending along this sewing line.

[0070]FIG. 9(b) and FIG. 9(c) show how many foundation cloths are sewed
by each of the first to fourth sewing lines 154, 156, 168, 170 and how
the foundation cloths are sewed.

[0071] As shown in FIG. 9(a), the inner surface of one foundation cloth on
the rear side in the figure, from among the two overlapping foundation
cloths forming the first chamber 162, is a silicone-coated coated cloth
172A. The outer surface of this foundation cloth abuts against the
occupant's knees and restricts the forward movement of the occupant.
Meanwhile, the inner surface of the other foundation cloth on the front
side in the figure, from among the two overlapping foundation cloths
forming the first chamber 162, is a non-coated cloth 174A that is not
coated with silicone.

[0072] The first chamber 162 may be constituted by the foundation cloth of
any weight, but the coated cloth 172A and the non-coated cloth 174A are
the two innermost cloths forming the first chamber 162. Cloths of
dissimilar materials may be used, provided they are at the inner surface
of the first chamber 162, and the materials at the front and rear sides
may be interchangeable.

[0073] With the above-described configuration, damage that can easily
occur in the first chamber 162 can be prevented. Since the first chamber
162 is the farthest from the inflator 122, it is a portion into which the
gas is supplied with the largest delay. When the cushion section 110 is
deployed, the folded or wound portion remains in the first chamber 162 to
the very end. Since the deployment of the cushion section 110 is thus
delayed, tension and twisting occur in other portions that are deployed
earlier, friction easily occurs between the inner surfaces, and the
damage easily occurs.

[0074] Accordingly, in the present embodiment, the portion where the
friction easily occurs is from the coated cloth 172A and the non-coated
cloth 174A as described hereinabove. This is done so because even if the
friction occurs between those dissimilar cloths, they can be prevented
from damage much more effectively than in the case where the friction
occurs between the cloths of the same kind.

[0075] The inner surface of the foundation cloth of the second chamber is
the coated cloth 172B, 172C on both the rear side and the front side, as
shown in the figure. The inner surface of the foundation cloth of the
third chamber 166 is the non-coated cloth 174B, 174C on both the rear
side and the front side, as shown in the figure. However, the coated
cloth is used on both sides for the outer surface (not shown in the
figure) of the foundation cloth of the third chamber 166.

[0076] FIG. 10 to FIG. 15 illustrate the steps of folding the cushion
section 110 shown in FIG. 9(a). As shown in FIG. 10, the cushion section
110 is initially folded a plurality of times or wound from the first
chamber 162 toward the third chamber 166. As a result, a roll section 180
is formed as shown by way of example in FIG. 11. FIG. 12 shows a state in
which the cushion section 110 is turned over so that the roll section 180
formed as shown in FIG. 11 faces toward the rear side as shown in the
figure.

[0077] As shown by way of example in FIG. 13, one end 180A of the roll
section 180 is folded back toward the side opposite that where the roll
section 180 has been formed. This will be referred to hereinbelow as the
first folding. FIG. 14 shows a state in which the tip of the one end 180A
of the roll section 180 that has been subjected to the first folding is
further folded back in the direction of both ends of the roll section
180. This will be referred to hereinbelow as the second folding. Those
first folding and second folding operations are performed, as shown in
FIG. 15, with respect to both ends 180A, 180B of the roll section 180.
The folding is thus completed.

[0078] FIGS. 16(a)-16(c) illustrate the deployment behavior of the cushion
section 110 that has been folded as shown in FIG. 15. FIG. 16(a)
corresponds to a view along an arrow F in FIG. 15. The deployment
proceeds in the order of configurations shown in FIGS. 16(a), 16(b), and
16(c). As viewed by the occupant seating in the driver's seat shown in
FIG. 1, the folded cushion section 110 has such a posture, and although
it is actually not seen by the occupant, the cushion section is oriented
as a substantially Q-like shape with respect to the occupant.

[0079] In the case of the cushion section 110 that has been folded or
wound as explained with reference to FIG. 10 to FIG. 15, the deployment
behavior is not the exact reversal from the very end to the very
beginning of the folding step. Thus, as shown by way of example in FIG.
16(a), the deployment (arrow 182) of the roll section that is formed on
the initial stage of the folding proceeds before the deployment (arrow
184 in FIG. 16(b)) in the left-right direction of the double fold
obtained by the first folding and second folding performed at the very
end of the folding step.

[0080] Since the roll section 180 is thus deployed in advance at a point
of time in which the double fold is still present, torsion is generated
in the cushion section 110. As a result, a damage 190 occurs on the
trajectory of the second folding line 188, from among the first folding
line 186 and second folding line 188 (only left side is shown in the
figure) located on the inner surface of the cushion section 110, as shown
in FIG. 9. In particular, since the first chamber 162 is positioned on
the innermost side of the roll section 180, it is not deployed till the
very end and friction easily occurs on the inner surface under the effect
of torsion. For this reason, the damage 190 most often occurs on the
trajectory of the second folding line 188 that is present on the inner
surface of the first chamber 162.

[0081] However, in the present embodiment, since the inner surface of the
first chamber 162 is formed from the dissimilar coated cloth 172A and
non-coated cloth 174A, the damage is unlikely to occur even when friction
occurs.

[0082] The idea of the present embodiment relating to the materials of the
inner surface of the cushion section 110 is described below. According to
the present embodiment, in the airbag of a configuration including one or
more chambers (for example, knee airbag 100), the airbag is folded or
wound, and a cloth is provided inside a chamber (for example, the chamber
162) at a location (for example, close to the damage 190) where the
unfolding or unwinding of the airbag proceeds slower than in other
portions.

[0083] The abovementioned configuration is selected because the
probability of damage is higher in the portions where the unfolding or
unwinding proceeds slower than in other portions.

[0084] The abovementioned cloth may be provided on the innermost side of
the folded or wound body at a position at a distance from the inflator
accommodated in the airbag.

[0085] The abovementioned configuration is selected because the folded or
wound state is maintained till the very end at such a position when the
airbag is deployed.

[0086] The abovementioned cloth may be a non-coated cloth (for example,
non-coated cloth 174A) that is not coated with silicone.

[0087]FIG. 17 illustrates a cushion section 210 having a diffuser 252
obtained by changing the diffuser 152 shown in FIG. 6. Only the
difference between the changed diffuser and that shown in FIG. 6 is
described below. The diffuser 152 shown in FIG. 6 has a tubular portion
153 having a rectangular cross section, whereas a tubular portion 253 of
the diffuser 252 shown in FIG. 17 has a trapezoidal cross section.

[0088] In other words, the diffuser 252 is formed by folding back
hexagonal cloths along any diagonal and stacking the substantially
congruent and left-right symmetrical trapezoidal cloths by taking the
diagonal along which the cloths have been folded as an upper base 254.
The portion corresponding to the lower base 256 of the trapezoid is sewed
to a foundation cloth 210A by the first sewing line 154. The inflator 122
is inserted together with the deflector 132 into the tubular portion 253
close to the lower base 256.

[0089] As shown in FIG. 17, the diffuser is folded back at both outer
sides of the portion corresponding to the lower base 256 of the diffuser
252 along the creases (first folding lines 186) that are substantially
orthogonal to the longitudinal direction of the diffuser 252.

[0090] With the above-described configuration, no choking occurs in the
cushion section 210 and the deployment proceeds rapidly. This is because
the lower base 256, which has a small length, does not engage with the
first folding lines 186, and the inflator 122 is inserted close to the
lower base 256, as a result of which the gas outlet ports are not closed.

[0091] FIG. 18 illustrates a cushion portion 210 having a diffuser 262
that is obtained by further changing the diffuser 252 shown in FIG. 17.
Only the difference between the changed diffuser and that shown in FIG.
17 is described below. An upper base 264 of the diffuser 262 shown in
FIG. 18 is longer than the upper base 254 shown in FIG. 17 and becomes a
tubular portion 263 that reaches the first folding lines 186, which are
the creases of the first folding. In other words, the first folding lines
186 are positioned on the inner side of both ends of the portion
corresponding to the upper base 264 of the diffuser.

[0092] With the above-described configuration, the portions of the upper
base 264 of the diffuser 262 engage with the first fold. However, since
the vicinity of the lower base 256 where the inflator 122 and the
deflector 132 are present does not engage with the first folding lines
186, no choking occurs. Meanwhile, rapid deployment is ensured since the
portions of the upper base 264 are increased in length in the course of
engagement with the first folding lines 186.

[0093] The idea of the present embodiment relating to the variation
examples of the diffuser is summarized below. According to the present
embodiment, in a knee airbag in which the cylinder-type inflator 122 is
accommodated in the internal diffuser 252, a roll section (for example,
the roll section 180) is formed by folding or winding in an
accordion-like or roll-like configuration in the knee airbag, and both
ends of the roll section are folded back to the center (for example, the
first folding), and the outlet ports of the diffuser are not engaged with
the folding lines (for example, the first folding lines 186). As a
result, no choking occurs.

[0094] Further, in the above-described variation examples, the tubular
portions 253, 263 are used, but a diffuser of a closed bag-like shape,
rather than the tubular shape, that is provided with a vent hole 270 to
introduce gas may be also used.

[0095] The preferred embodiments of the present invention are described
hereinabove with reference to the appended drawings, but the above
embodiments are merely preferred examples of the present invention, and
other embodiments may be also implemented or executed using various
methods. In particular, the present invention is not limited to the
shapes, dimensions, and arrangement of the components illustrated in
detail in the appended drawings, unless specific limiting description to
the contrary is provided in the specification of the present application.
Further, expressions and terms used in the specification of the present
application are employed for descriptive purposes only, and the present
invention is not limited to these expressions and terms unless
specifically stated otherwise. For example, all of the embodiments are
explained using a knee airbag, but the present invention may be also
applied to a variety of airbags provided in a vehicle, such as a driver
seat airbag, a passenger seat airbag, a side airbag, and an inflatable
curtain airbag.

[0096] Therefore, it is clear that a person skilled in the art could
conceive of various variation examples or modification examples without
departing from the scope defined by the claims, and those variation
examples and modification examples are also construed to be included in
the technical scope of the present invention.